Seismic and geological data suggest that the closed geodepression of the Arctic Basin emerged not earlier than in the Late Jurassic – Cretaceous on the site of a vast continent, gradually flooded by the sea. Until the mid-Mesozoic, most of the Arctic Ocean was an ancient platform (Arctida), reworked to varying degree by uneven folding and continental rifting, which resulted in the formation of a submeridional system of grabens and horsts in the Central Arctic Region, indicating extension processes and block movements. Further subsidence of the basin led to the formation of the recent Arctic Ocean not earlier then in the Neogene. An obligatory morphological and geological feature of the emerging ocean is the presence of the shelf–slope–deep-sea plain triad. The evolution of the sedimentary cover of the Arctic Ocean is illustrated by a set of seismic facies maps compiled after analyzing interconnected seismic facies lines that intersect major morphostructures.

The Ayano-Shevlinsky pericratonic basin along the southeastern margin of the Aldan-Stanovy shield, the Siberian Platform, contains isolated outcrops of variegated Upper Riphean, Vendian, Cambrian, Ordovician, Silurian, Devonian and Carboniferous clastic-carbonate deposits, basalts, granitoids and gabbroids of similar formational type as the deposits of the Yudoma-Maya pericratonic basin located to the north. Stratigraphic hiatuses of varying durations are common throughout the section. Deposits are arranged in folds of different morphologies, from brachiform to isoclinal.

As a result of recognire conodont studies, the presence of deposits of two local and one regional conodont zones was established in the outcrop of 229 of the River Kozhym, which made it possible to the regional stratigraphic units – Lolashor, Filipp’’el’ and Marshrutnyj regional stages, previously identified in the outcrop mainly by lithological features.

The paper presents results of the petrological and geochemical study of the Maldzhangar carbonatite located in the southeastern part of the Billyakh zone of tectonic melange (southeastern periphery of the Anabar shield). According to results of the U-Pb pyrochlore dating (SHRIMP II), the carbonatite generated about 167 Ma ago. It is established that the carbonatite is represented by three mineral types: calcite, dolomite and calcite-dolomite. The carbonatite composition evolved from early calcitic to calcite-dolomitic and dolomitic. The geochemical similarity of all the varieties of carbonatite indicates that all of them originated from the same melt. The carbonatite is enriched in a wide range of elements: LREE, Nb, Sr, As, MREE, Th, Ba, Ta, Y, Zn, Pb, and Au. Carbonatite geochemical features closely match the mineral composition. LREEs are the major and useful component of commercial interest. Nb, Ta, Y, P, Sr, and Ba may be of commercial interest as minor components. The data obtained suggest that the Maldzhangar carbonatite massif is a source of rare earth and rare metal elements.

The article deals with the first discovery of a diamond in Lower Permian bedrock in the Sylva River headwaters within the eastern wing of the Yuryuzan-Sylva depression. The work is based on results of authors’ studies, generalization of materials, both on the diamond potential of the Cis-Ural Trough and the West Ural structural megazone, and on geology and petrography of the host rock assemblages, their structural and tectonic position in the zone of influence of the Main West Ural Thrust. The paper uses results of studies on a TESCAN VEGA LMS scanning electron microscope with an Xplore 30 energy-dispersive attachment from Oxford Instruments and a URS-55 X-ray unit in an RCD chamber in the URSMU laboratory. The mineralogical and petrographic study of coarse clastic rocks hosting the diamond, identified as tuff breccias, showed their fluid-magmatic genesis, as evidenced by the textural, structural and mineralogical features of the rocks, including drop-shaped elliptical volcanicglass segregations, pulp-like finely dispersed nature of the groundmass (binding material), ungraded, weakly rounded to acute-angled fragments of igneous and sedimentary rocks, occurrence of such accessories as kyanite, rutile, monazite, zircon, apatite, titanite, gold, chrome spinel, moissonite, magnetic and glass microspherules. The data obtained indicate the probable phreatic volcanism, which led to the transportation of the diamond and its satellites to a weakened activated zone in the forefront of the Main West Ural Thrust.

In the paper, an attempt is made to highlight characteristic features in the formation history of diamondiferous placers in this area based on the analysis of the distribution of the mean size of diamonds in Cretaceous–Cenozoic coastal economic diamondiferous deposits of the Atlantic coast, South Africa (SA).

Data on the U-Pb isotopic age of zircon detritus from leucoxene-quartz ores of the Yaregsk oil-titanium deposit, which indicate a sharp predominance (92%) of Riphean dating in the range of 900 to 1600 Ma, have been obtained for the first time. Their comparison with the published data on zircons from the Pizhemsk titanium deposit proves that the denudation products of the Riphean rock complexes were the dominant source of clastic material for both placers. Insignificant amount of Late Archean detrital zircons in the ore of the Pizhemsk deposit confirms that the Pizhemsk deposit provenance area differed from that of the Yaregsk deposit in a deeper erosional truncation of Riphean strata. It is shown that the isotope-geochronological data do not contradict the hypothesis that the Yaregsk oil-titanium deposit belongs to the two-stage sedimentary-naphthide-epigenetic leucoxene type.

Ore deposits related with mafic-ultramafic mantle magmatism contain sulfide Cu-Ni ± PGE deposits, but in many cases without PGE. Reasons for such a difference in mafic-ultramafic mantle magmatism are most often not studied, but tectonic petrological understanding of this phenomenon requires explanation, both from a scientific point of view and for economic purposes, particularly since such deposits are of strategic importance. In the proposed paper, an attempt is made to provide a petrological tectonic and isotope geochemical explanation of the reasons for possible lack of platinum group elements for sulfide Cu-Ni ± PGE deposits.